Noninvasive cardiac index monitoring in gunshot wound victims

To evaluate a bioimpedance device for the noninvasive measurement of cardiac index (CI) against standard thermodilution measurements in patients with gunshot wounds.

A prospective open-label performance evaluation was done using a convenience sample of gunshot wound victims initially treated in the resuscitation area of a high-volume, urban ED. After initial resuscitation, patients had a flow-directed pulmonary artery catheter placed for thermodilution cardiac output (CO) measurements. The CO measurements were made in triplicate and averaged. Estimates of body surface area were used to convert these measurements to CI estimates. Electrodes for bioimpedance measurements were placed as soon as practical after ED arrival. Simultaneous measurements of CI using the bioimpedance device were made as clinically indicated during each patient's hospital course.

There were 54 patients studied, with an overall mean (+/- SEM) age of 32 +/- 3 years, Revised Trauma Score of 6.7 +/- 0.4, and Injury Severity Scale score of 22 +/- 3. There were 42 survivors and 12 nonsurvivors. The CI as estimated by bioimpedance correlated well with that measured by thermodilution (r = 0.79, p < or = 0.02). The precision of the invasive and noninvasive measurements was 1.1 L/min/m2; the bias was -0.011 L/min/m2. In 24 patients with thoracic injuries requiring tube thoracostomy or thoracic surgery, the correlation of the 2 devices was r = 0.71 with precision and bias of 1.4 L/min/m2 and -0.018 L/min/m2, respectively.

Cardiac index can be noninvasively estimated in acutely injured patients with gunshot wounds using a bioimpedance device. Further study of bioimpedance measurements as a guide to volume therapy is warranted.